The present invention generally relates to breast pumps and specifically to an improvement in manually operated breast pumps.
Increasing numbers of women are choosing to feed their babies with mother's milk and it is widely assumed that both the preference of the natural product over substitutes as well as the bodily contact during breast-feeding are best for the infant. Frequently, however, there is an at least temporary need for a breast pump; for example, a mother who delivers her infant prematurely will pump her breast so that the colostrum and milk can be fed to the premature infant having a particular need for the protective factors known to be contained in colostrum and normal mother's milk.
Other circumstances that indicate the use of a breast pump include temporary hospitalization of either mother or child, a flat or inverted shape of the nipple as well as other physiological factors and, last but not least, the problems of supplying an infant with mother's milk when the mother continues or commences to work outside the house.
Two main types of conventional breast pumps are to be distinguished depending upon how the pressure reduction (also called "negative pressure" or "suction pressure") within the suction bell that is put onto the breast will be generated, i.e. either by means of an electrical motor or manually.
The term "suction bell" is used herein to refer to any open-ended structure having an opening at the end of a hollow and generally convergent structure with a linear or curved taper providing sufficient space to fit onto a breast around the nipple or teat without having direct contact with neither teat nor areola; of course, a suction bell is a structural feature common to motorized as well as manually operated breast pumps.
Another common feature of most breast pumps is some kind of reservoir or space for holding the pumped-off milk. Thus, a conventional pump comprises the suction bell connected with a reservoir, such as a bottle, and with a source of negative pressure for causing a sufficient but not overly strong and preferably easily controllable suction; typically, such suction is defined by the ambient atmospheric pressure minus the "negative pressure" or "suction pressure" of, say, 0.01 to 0.3 bar.
In all conventional breast pumps for manual operation suction is produced by means of a hollow space or cavity having a variable enclosed volume; a typical example of such a suction means is a rubber ball or bulb that can be manually compressed and tends to recover its original shape when not compressed by hand. Such a ball or bulb, optionally provided with a one-way valve, can be connected directly with a suction bell to serve as a simple breast pump if the internal volume of the suction bell is sufficient so that it can act as a temporary milk reservoir.
A main disadvantage of manually operated breast pumps having such rubber-ball-type suction means is that sterility cannot be maintained and certainly not visually controlled. In that respect breast pumps of the "coaxial" type disclosed in U.S. Pat. No. 3,977,405 issued Aug. 31, 1976, to Shozaburo Yanase provide the advantage of being made of a sterilizable transparent polymer, e.g. a polycarbonate, or of ordinary glass so that sufficient sterility can be easily obtained, e.g. by boiling in water, and visually controlled.
Briefly, a prior art coaxial breast pump of the type disclosed in the U.S. Patent to Yanase just mentioned works in the manner of an inversely operated syringe such as disclosed in U.S. Pat. No. 3,886,928, issued June 3, 1975 to Sarstedt except that the piston element is hollow and carries the suction bell. Hence, the mother's breast serves to close the hollow piston element of a breast pump of the coaxial type.
Generally, the coaxial-type breast pump disclosed in the U.S. Patent to Yanase comprises an inner and an outer cylinder and a packing on the outside of the inner cylinder to seal up a clearance between the inner and outer cylinders; the inner cylinder has two open ends, one end being divergent so as to form a suction bell which is put against a breast while the other end is inserted into the outer cylinder and displaced therein. The outer diameter of the inner cylinder is smaller than the inner diameter of the outer cylinder to permit the displacement of the inner cylinder in the outer cylinder and the outer cylinder is a container with an open end and a closed end.
Prior art breast pumps of this coaxial type have been found to suffer from two disadvantages: when the pump is used in an erect sitting position, i.e. with the thorax in an upright or substantially vertical position, the longitudinal axis of the outer cylinder will be nearly horizontal or slightly inclined, say at an angle of 10.degree. to 20.degree.. In such a position of the outer cylinder--which serves as the milk reservoir--even a minor amount of milk will fill the reservoir to the extent that back-flow of the milk from the inclined reservoir towards the breast will occur.
Such back-flow is quite undesirable because bacterial, viral or other contaminants on the skin will be washed into the milk. Further, as back-flow of milk may cause an uncomfortable sensation, the mother using such a pump will either tend to incline her thorax in a forward direction so as to increase the angle between the teat axis and the horizontal, or she will attempt to tilt the outer cylinder relative to the teat axis; as teat and areola of the breast of a nursing mother are extremely sensitive, such tilting of the milk reservoir of a coaxial pump is neither generally feasible nor normally free of discomfort. Almost needless to say that a coaxial pump of the type disclosed in U.S. Pat. No. 3,977,405 cannot be used at all when the thorax of the person using the pump is inclined backwards such as when at rest on a bed or in a backwards inclined chair.
The other main disadvantage of prior art coaxial breast pumps as disclosed in U.S. Pat. No. 3,977,405 is a substantially rigid motional coupling of the inner and the outer cylinder when the latter is tilted. In other words, any voluntary or involuntary motion of the user's hand that will cause "tilting" of the longitudinal axis of the outer cylinder (i.e. any angular change of the position of that axis relative to a line of reference, e.g. the breast or teat axis) will cause about the same tilting of the inner cylinder and, thus, of the longitudinal axis of the suction bell. This, in turn, will, at best, cause an irregularity in the distribution of the pressure of contact between suction bell and breast or, at worst, a tilting stress on the teat and/or the areola which in many instances will cause pain in these most sensitive breast areas.